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**Shuriken** · 11-19-2006, 02:21 PM

Don't chase your tail. Pick one problem and work on it until you're satisfied that you fixed it. Then move on.

A.
Always best to start from stock and only mod 1 thing at a time. You say the airbox and exhaust are the only thing not stock. Considering your higher-flow 4-1 and a hole in the airbox, that would seem to me that you would be more likely to have a lean combustion condition. You have 2 mods (1-pipe, 2-airbox) that are for leaning the mixture. Keep that in mind.

B.
Also, you say the bike runs crappy on the top end, 6k-up. Keep in mind that at that RPM range, the needle jet and jet needle are in play. Not sure what year your bike is, but my 79sf has adjustable jet needles. Check yours. Set them at stock position.

C.
Read the spark plugs. Take the bike out and wind it up until it starts to get into the crappy range and then kill the engine, coast to a stop, and then remove the spark plugs to see what color they are. I would be surprised if you saw dark or black plugs.

D.
If one plug was black and the other plugs were not, I would think either the plug could be intermittent/bad, and/or that corresponding carb could be rich.

Just some thoughts.
Ben

**OneHand** · 11-20-2006, 01:34 AM

It's not even running. That's just revving it when stationary. (Dont like to do it, but don't like to ride when it's not right either)

The only variable I can think off now, must be the pick -ups. If all else fail, I'll repair the old set (broken wire) and put it back with the new sensor that seems to be straight.

I've now gone from bad to worse. At least it was rideable be4, even if it was on 3 cylinders.

At least I know that all 4 cylinders are getting spark and fuel. All 4 headers getting hot about equal heat, where #2 was colder than the others before.

Thx

1H

**TopCatGr58** · 11-20-2006, 08:43 PM

Hey OneHand,

I meant to post this yesterday, forgot!

Pickup coil gap is 0.7mm, or 0.0275".

I think the timing ROTOR is the reluctor?? But, if it's wobbly, not good. Have you inspected the centrifigual advance mechanism, make sure the timing plate rotates freely and easily, that the weights can spin outward and advance the plate? Have you checked the timing with a light, at low speed and around 5Krpm to verify that you're able to get max. timing advance?
Vacuum advance working properly?!
T.C.

**OneHand** · 11-20-2006, 11:53 PM

And the light goes on!!!

Hi TC

I replaced the wobbling ROTOR with the spare one. Did not know what the springy things were on the old one. When I first read 'centrifugal' advance, it hit me like a hammer! The new one must be off a newer model ... XJ maybe??? Does not have that.

Vacuum advance was also replaced with the newer one. Parts are definitely in better condition as the PO dropped it on its left side, smashing the cover, bending the rotor, and grazing the vacuum advance. Thought it was a simple take off and replace...

Thx

1H

**OneHand** · 11-21-2006, 04:57 AM

Coming to think of it, might not be that at all? I had the old, dancing rotor with the new p/u coils and it did the same.

Think I'll have to go back to the old P/U's to see if that isolates the problem, then work from there again.

Did the newer ones also have the centrifugal advance, or was it done electronically? Seem to remember reading something like that, but can't be sure...

Havn't got a timing light, will have to go get one after work.

Thx, 1H

**skids** · 11-21-2006, 10:29 AM

If you have the newer xs11 ignition, I think your black box will be the 4RO model and you will not need the ballast resistor. The associated pickups are different because the advance (or retarded timing, depending on how you look at it) is controlled by the black box. There is a vacuum hose to the timing mechanism, but somehow it works differently. I think the pickup coils are larger as well. I wish I could describe it all better, but I have not had any trouble with the H model. Note that you cant mix black boxes and pick-up mechanisms from new and old models.

**TopCatGr58** · 11-21-2006, 09:20 PM

Hey One Hand,

Like you said, it's probably not necessarily the PU coils so much as the Wobbly Rotor, and possibly stuck cent. advance mechanism. As Skids said, the newer 81 machine uses a different TCI, controls the Cent. Adv. electronically, so only uses the vacuum module, then in 82, another TCI change, ALL electronic, no cent. adv. mechanism or vacuum slider, just a vacuum sensor box.

SO, with using a newer rotor without cent. advance, you are NOT getting enough timing advance, cause your 79 TCI model 2H7-xxxxx needs the rotation of the timing plate to induce the advance! You can't use the newer timing parts without using the newer TCI! So...you'll probably need to find a replacement for a 78-80 machine! Then, it should be able rev past 6-7K!
T.C.

**pggg** · 11-22-2006, 02:01 AM

For the wobbly rotor, here's a test - Each ignition coil has it's own pulser coil. Swap the pulser connections at the plastic plugs behind the r/h sidecover, and assuming there's weak spark on 2 plugs, testing for spark at the HT leads you can tell if the fault swaps sides.

**pggg** · 11-22-2006, 02:33 AM

P.S. The best way to test for spark is by feel. Be sure to moisten the tip of the finger. I find you get better voltage estimates using your index finger. Just lightly touch the sparks as the motor spins using the starter motor and test all 4, you'll immediately know which wires are down on power.

**OneHand** · 11-22-2006, 04:52 AM

And I'll make sure i'm not wearing sneakers, and standing in a puddle of water...

Brought the rotor in to work today to see if the guys in hte machine shop can mayby straighten it out.

With the 81 rotor, I definitely got spark on all 4, as all the headers warmed up equally. Also the gap was good at about 0.63mm (biggest feeler gauge I've got) Then measured the rotor compared to the old one. size difference of about 2mm, which means the gap will be slightly bigger on the old rotor. Will adjust when I put it back in. If all else fails, I'll put the old PU coils back.

1H

**OneHand** · 11-23-2006, 12:05 AM

WHOOAA NELLY!!!!

Fixing the rotor and air gap seems to have solved the problem!

Had the guys at work straighten out the rotor with centrifugal advance, and put it in yesterday after work. Set the air gap to 0.63mm, then took it out for a spin...

Cant believe what difference an extra cylinder makes! Pulling strong and true from 2.5K right to redline, with a serious kick about 5K. Opening up from 4K in 5th, up to 6K in no time... (Still waiting for speedo from UK!)

Maybe still a small hesitation when pulling off, but should be able to solve with proper vac sync and color tune. Not even sure if I should bother changing the jets, but will see what the plugs look like after I ride a bit.

Just confirms what has been said many times on this site. Work on it yourself! Most shops don't have a clue on how to fix these old bikes!!!

Thanx to all for helping out, and all the suggestions. I'm sure some more questions will come up with the next part of the restoration...

1H

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